Device for making electricalconductivity tests on tubular articles



April 1948; G. R. GREENSLADE 2,440,044

DEVICE FOR MAKING ELECTRICAL-CONDUCTIVITY TESTS ON TUBULAR ARTICLESFiled March 24, 1943 4 Sheets-Sheet 1 April-20, 1948, a; R. GREENSLADE2,440,044

DEVICE FOR MAKING ELECTRICAL-CONDUCTIVITY TESTS ON TUBULAR ARTICLESFiled March 24, 1945 4 Sheets-Sheet 2 P" 1948- G. R. GREENSLADE DEVICEFOR MAKING ELECTRICAL-CONDUCTIVITY TESTS ON TUBULAR ARTICLES 4Sheets-Sheet 3 Filed March 24, 1945 INVENTCR ran/611R. Greenslade 1 I.mm

$1 NQ AE April 1948- p G R. GR-EENSLADE ,440,

DEVICE FOR MAKING ELECTRICAL-CONDUCTIVITY TESTS ON TUBULAR ARTICLESFiled March 24, 1945 4 Sheets-fSheec 4 Patented Apr. 20, 1948 DEVICE FORMAKING ELECTRICAL- CONDUCTIVITY TESTS ON TUBULAR ARTICLES Grover It.Greenslade, Scott Township, Allegheny County, Pa., assignor to Flannel-yBolt Company, Bridgeville, Pa., a corporation of PennsylvaniaApplication March 24, 1943, Serial No. 480,285

4 Claims.

This invention relates to the testing of metal articles and, inparticular, to the testing of hollow or tubular articles for thepresence of a defect such as a fracture resulting from stresses to whichthe article is subjected in service. My invention is, specifically, animprovement on the testing device disclosed in my Patent No. 2,091,634.

The present invention, like the apparatus of the patent aforementioned,utilizes the change in the resistance of the article being tested uponthe occurrence of a fracture therein. This change in resistance isdetected by circulating a current through the article and observing thevoltage drop between a succession of pairs of equally spaced pointsalong the length of the article. The improvement with which the presentinvention is concerned is in the manner of and means for circulatingcurrent through the article under test.

In a Preferred embodiment and practice of the invention, I provide atesting device adapted to be inserted within a hollow or tubular articleto be tested, said device having current contacts adapted to engage theinterior surface of the article, said contacts being connected to asuitable source of current which may either be external to the device ormounted therein. In addition, the device is provided with a pair ofvoltage contacts also adapted to engage the interior of the articlebeing tested, said contacts being connected to an indicator such as avoltmeter or galvanometer. one of numerous different forms some of whichare illustrated in the accompanying drawings. Further novel features andadvantages of the invention will become apparent during the followingdetailed description and explanation referring to said drawings. In thedrawings,

Fig. 1 is a longitudinal section through one form of testing deviceembodying the invention and including a, self-contained current source;

Figure 2 is a diagrammatic view showing in longitudinal section atubular or hollow body having the testing device inserted therein;

Figure 3 is a view similar to FigureZ showing a slight modification ofthe construction of the testing device;

Figure 4 is a diagrammatic view showing the article under test in endelevation with the testing device of Figure 3 inserted therein;

The invention may take any Figure 5 is a view similarto Figure 4 showinga modified form of testing device for use in articles having rectangularopenings therein instead of round holes.

Figure 6 is a longitudinal sectional view through a a tubular article tobe tested with a modified form of testing device inserted therein;

Figure 6a is a diagram of the circuit connections used with the testingdevice of Figure 6;

Figure '7 is a side elevation of a modified form of current contactadapted to be used with the testing device of Figure 6;

Figure 7a is a sectional view taken along the plane of line VIIa-VIIa ofFigure 7;

Figure 8 is a partial longitudinal section through a further modifiedform of testing device, specificallya device intended for articleshaving relatively small bores such as staybolts for locomotive boilers;

Figure 9 is a transverse section through the device of Figure 8 taken online 1XIX thereof;

Figure 10 is an exploded view illustrating the assembly of a furtherform of testing device;

Figure 11 is a side elevation thereof after the initial stage ofassembly;

Figure 12 illustrates a further step in the formation of the completedevice;

Figure 13 illustrates a still further step which may if desired be thefinal step of enclosing the device in a sheath of insulation;

Figure 14 is a side elevation showing the de-,

vice enclosed in .a protective metal tube;

Figure 14a is a transverse section through a further modification oftesting device;

Figure 15 is a partial longitudinal section through a device to betested showing another form of device inserted therein;

Figure 16 is a central longitudinal section through the forward end ofthe device of Figure 15;

Figure 17 is a transverse sectional View on the plane of line XVII--XVIIof Figure 16; and

Figure 18 is a diagrammatic view illustrating a further m-odification oftesting device.

Referring now in detail to the drawings and, for the present, to Figures1 and 2, one form of testing device emboodying my invention is indicatedgenerally at In and includes a tubular casing or shell ll of such sizeas to be capable oi insertion into the articles to be tested, having aclosure disc I2 screwed into the forward end and a removable cover I3similarly secured to the rear end. Bushings I4 of insulaitng materialhave their outer ends threaded into tapped holes through the walls ofthe casing I I and projecting inwardly thereof. The bushings may bespaced along the length of the casing at a convenient distance apart andare adapted to receive contact points I5, I 6, I! and I8, the ends ofwhich proiect outwardly of the casing II and are yieldingly urged totheir outermost positions by springs IS. The contact points haveshoulders 20 engaging contracted necks formed at the outer ends of thebushings Hi to limit their out?- ward movement. Closure discs 2I arethreaded into the inner ends of the bushings I4 to secure the springs I9in place. The closures 2! also serve as a convenient point for thattachment of circuit conductors since ,theyare in constant electricalcontact with the points through the springs I9 which are of metal.

Points I5 and I8 serve as current contacts and the points I6 and I! asvoltage contacts. All the points engage the interior of a hollow ortubular article to be tested such as that indicated at 22 which may be ahollow axle, locomotive crank pin or the like. As indicated by thecurrent flow lines 23 in Figure 2, an electric current flows between thepoints I5 and I8, through "the metal or otherelectrically conductingmaterialof which the article or member 22 'is composed. Current may besupplied to the points and I8 from any suitable source. In the device ofFigure 1, I provide a current source in the form of a dry cell 24positioned in the rear or handle end of the casing II. An insulatingdisc 25 secured transversely in the casing II by screws 2.5 is providedwith a central'contact .21 adapted to be engaged by the center terminalof the cell 24. A disc '28 of insulating material resting on the coverI8 has a leaf spring 29 which keeps the center terminal of the cell inengagement with the contact 21 and also serves as a contact engaging thebottom of the cell.

A rheostat 3B is mounted in the casing II in any convenient manner andpreferably comprises a disc '3I of insulating material having contactpoints 32 connected at intervals to -a resistor 33. A rotating contactfinger 34 is secured to a shaft 35 projecting radially from the casingII and having a suitable operating knob thereon (not shown).

As clearly shown in Figure 1, the point I5 is connected directly by asuitable conductor to the spring 29. The point I8 is similarly connectedto one end of the resistor 33 while the contact finger 3:1 is connectedto the contact 21. It will thus be apparent that when the contacts I5and I8 are bridged by electrically conducting material, a current willflow through the latter depending on'the adjustment of the finger 34 ofrheostat 39. The points IS and I are connected directly by suitableconductors to a voltmeter 38 mounted on the rear or handle portion ofthe casing I I.

To use the device it), it is simply inserted in the interior of thehollow article to be tested, such as that shown at 22, with the contactpoints in engagement with the interior surface thereof. After the devicehas first been inserted, the rheostat 3 9 is adjusted to produce asuitable reading on the voltmeter '36. It will be understood thatcurrent flowing between the contacts I5 and I8, as shown in Figure 2,results in a voltage drop from point to point along the path between thecontacts. The reading on the voltmeter, of course, is the voltage dropbetween the points on the article 22 engaged by the contact points Itand IT. The exact value of this voltage is immaterial so long as itprovides a readily readable indication on the voltmeter such that anyvariation may be immediately perceived.

When the rheostat has been adjusted to give such reading, the device Itis moved longitudinally of the article 22, maintaining contact of thepoints with the interior of the article. So long as the material of thearticle 22 between the points on the interior thereof engaged by thecontact points It and I1 is without any deiect such as a crack orfracture, the voltage drop betweenthe points It and I! will remainconstant since the current circulating through the article betweencontacts I5 and I8 is constant and the resistance of the article betweenthe position of the device. If the movement of the idevicelongitudinally into the article being tested resultsin the points I6 andI"! being located on opposite ,sides of a defect such as a fracture orcrack, aj'variation in the reading of the voltmeter 36 will immediatelybe perceived. This is because the presence of a defect such as afracture reduces the sectional area of the metal available for carryingcurrent, little or no current passing from one surface of a transversefracture to the other. The increased resistance, of course, reduces thetotal current flowing. The voltage drop between the contacts I5 and I 8,however, remains substantially the same. -'I'here is a redistribution,however, of this total voltage dropso that a greater portion of itoccurs between points I6 and H, the drop between the points I5 and I Sand I1 and IB being correspondingly reduced.

The device I0, when used in the manner just explained, indicates thepresence of a defect adjacent the plane through the contact points andthe axis of the article being tested. For a complete test, therefore, itmay be necessary to insert the device at various angles. By this mode ofmanipulation, the angular location of a defect about the axis of anarticle may be determined as well as the location thereof relative tothe axial length. If the angular location of a defect about the axis ofthe article is of little or no interest, the form of device shown inFigures 3 and 4 may be preferred since itindicates a defect on onepassage through the article regardless of the angular location thereof.The testing device indicated at III in Figures 3 and 4 is similar tothe'device I0 except that the contact points are disposed on a helix, i.e., are spaced angularly about the circumference of the device and alongthe length thereof. As a result of this construction, current flowsthrough the article 22' along paths 23 in both directions around thehole or bore through the article. The resistance of practically any pathalong which current may fiOwbetween the'points I5 and I8 would beincreased by the presence of a defect such as a transverse fractureregardless of the location thereof about the axis of the bore throughthe article. This change in resistance will be immediately reflected ina change of the voltage drop between the points I6 and I1 as indicatedon the voltmeter 36, as the device II! is moved along the bore throughthe article 22.

It will be seen from the foregoing that the current supplied fortesting, according to the present invention, is confined to theparticular article being tested and to only a relatively small portionof the length thereof. It is thus possible to use a current source oflow capacity such as a dry cell, and the device may, therefore, beentirely self-contained. A separate source may be used as well, however,merely by extending to such source the leads shown connected to theterminals of the cell.

Figure 5 illustrates a modified form of testing device 31 adapted foruse in testing articles such as that indicated at 38 having an openingtherethrough of non-circular shape. similar in all respects to thedevice l except in the shape of the casing forming the body andenclosure thereof. a v

Figure 6 illustrates a further form of testing device 39 comprisingabase 40 having discs 4| and 42 secured to each end thereof by screws 43but insulated therefrom. The base 40 may be of any suitable material butthe discs are of, metal and are provided with conducting bristles 44composed of suitable material such as wire, adapted to engage theinterior of an article to be'tested such as that indicated at 45. Thebase 49 has brackets 46 at theends thereof, the upstanding portions ofthe brackets having slots adapted to receive screws 41 threaded into ablock of insulation 48. The block 48 has contact points 49 and 50embedded therein so as to engage the interior of the article 45. Springsserve to hold the contact points yieldingly against the interiorof thearticle-45. The device 39 may beprovided with any convenient form ofhandle (not shown) to facilitate manipulation thereof.

As shown in Figure 6a, the discs 4| and 42 with their bristles 44engaging the interior of the article 45 serve as current contacts whilethe points 49 and 5|] serve as voltage contacts. The disc 4| has a hole4|a therethrough to admit leads (not shown in Figure 6) extending to thedisc 42 and contact points 49 and 59. The discs 4| and 42 are connectedin circuit with a current source 52, a control rheostat 53 and a switch54. The points 49 and 50 are connected in series with a standard cell55, a galvanometer and a switch 51.

The device 39 operates on the same theory as the device I!) but theoperating procedure is slightly different. With the device inserted inthe article as shown in Figure 6, the rheostat 53 is adjusted afterclosing the switch 54, to give a zero reading on the galvanometer 55when the switch 51 is closed. In other words, the voltage drop betweenthe points 49 and 59 caused by the flow of current between the discs 4|and 42 through the article 45 is made equal to the voltage of thestandard cell 55. When the adjustment has been made, the device is movedalong the bore through the article 45 with the switches 54 and 51closed. Any variation of the resistance of the article between thepoints 49 and 59 such as would be caused by a partial fracture 58immediately shows up on the galvanometer 56. Such a definite reading onthe galvanometer as contrasted with the normal zero indication afiords aready signal to the user of the presence of a defect.- The altereddistribution of the The device 31 is discs 4| and 42 of Figure 6. Discs6| of insulating material have radial recesses adapted to receivecontact brushes 62 of carbon or similar conducting material. Springs 63disposed in the reoesses normally urge the brushes outwardly andremovable pins 64 passing through slots in the brushes limit theiroutward movement. The contact faces of the brushes are beveled tofacilitate the insertion into the bore of a tubular member to be tested,of a testing device having the modified type of current contacts. Asshown in Figure 7a, the discs 6| have screw holes for attachment to theends of' the member 40 in the same manner as the discs 4| and 42.

Figures 8 and 9 illustrate a further type of construction particularlyadapted for devices having holes of small bore such as staybolts. Thistype of device indicated at 65 comprises a metallic casing or tube 66, aliner 61 of insulation and conducting strips 68 and 69 having contactpoints 19 projecting outwardly therefrom. The casing 68 and liner 61have holes spaced therealong to admit the contact points 10. Inassembling a testing device of this type, the liner 61 is positionedwith its holes in alignment with those in the casing 66, The contactstrips 68 and 69 are then inserted in the liner and adjusted so thattheir contact points are in alignment with the holes in the liner andeasing. A separator strip ll of insulating material is then insertedbetween the strips 68 and 69 and forces the points 70 outwardly throughthe holes in the liner and casing. The strips 68 and 69 are bentoutwardly where the points 1|] are attached, thereby providing aresilient engagement of the points with the interior of a tubular memberbeing tested.

This device as shown with but two contact points 19 spacedlongitudinally, and oriented apart, may be used for articles havingholes of small diameters, in a circuit such as that shown in Figure 18.It may, however, be used in connection with the circuit as shown inFigures 1 and'6 by supplying another pair of terminals H! withadditional strip-spring members such as 68 and 69, by passing insulatedlead wires from the additional pair through any of the spaces shown inFigure 9 within the insulating tube 61. In applying the device ofFigures 8 and 9 in the latter cases, there is, of course, a somewhatdifferent orientation of the contact points from that which is shown inFigures 1 and 6a.

Figures 19 through 14 illustrate several steps in the manufacture of aslightly different type of device. Contact strips '12 having points 13secured to bowed-out portions near the ends there-- of are laid one onthe other with strips 14 of insulation therebetween. A tapering block ofinsulation i5 is applied to one side of the assembly of strips, theconducting strips 12 and insulation strips 14 being stepped backsuccessively from current as a result of the presence of the fracture 58is clearly shown in Figure 6 in which flow lines 59 indicate the normalcurrent distribution through the sound portion of the article while flowlines 60 show the distribution which results from the presence of afracture.

Figures '7 and 7a show an alternate form of current contact adapted tobe substituted for the the thick end of the block. When the parts havebeen properly assembled, they form an elongated member of approximatelyrectangular-section at all points, having radially projecting contactpoints spaced therealong. If it is desired to have the contact pointspositioned on a helix as in Figure 3, the assembled strips are given atwist of 180 as indicated at 16. A wrapping of insulating tape 11 isthen applied as shown in Figure 13 and the device may be used in thatform. As a further protection, however, a metal casing 18 having holestherein, for the points 13 may be applied. It will be understood thatthe casin 18 must beformed up from the fiat around the core of thedevice shown in Figure .13 and the joint between the abutting edgesclosed in any suitable manner-as by soldering or welding.

Figure 14a illustrates a further modified construction which may be usedeither in devices such as those shown in Figures 1 through 6 for testinglarge articles or in devices such as those of Figures 8 through 14 forsmaller articles. According to this modification, a cylinder 80 of anysuitable material has recesses 8i spaced along the length thereof andalso circumferentially, adapted to receive contact points 82 urged out-Wardly by springs 83. The recesses are lined with insulation and asheath 84 of insulation surrounds the cylinder .80. A protective casingof metal 85 encloses the entire device. Radial holes 8I a admit leadsfrom the points 82 to a central bore through the cylinder 80 forconnection to current supply means and indicator as in Figure 1. It willbe understood that thecontact points 82 which are farthest apart serveas current contacts while the other contacts are voltage contacts.

Figures 15 through 17 illustrate a furthermodification of testingdevice. According to this modification, a cylinder 86 of insulatingmaterial has spaced slots 81 milled therein, The slots have fiat bottomsthe portions of which are at 90 to each other as shown :in Figure 1'7and have segmental brushes 81a disposed therein. The brushes includeblocks which are normally urged outwardly by springs 88 disposed inradial recesses .89 formed in the cylinder 85. Outward movement of thebrushes is limited by screws 80. The brushes 31a have bristles 9Isimilar to those shown at M for engagement with the interior of a hollowor tubular member to be tested such as indicated at 92.

The brush blocks are so disposed about the member :86 that theirbristles engage the member 92 throughout substantially the entire innercircumference thereof.

The cylinder 86 also has radial recesses 93 as shown in Figure 16 spacedalong the length ther of and 180 apart on the periphery thereof,

adapted to receive contact points 94. The points 94 are normally urgedoutwardly by springs 95 and are reciprocable in bushings 96 threadedinto the recesses 93.

It will be apparent that the brushes 810. may

be connected to a suitable current source and control device, in themanner indicated in Figure 1, by leads extending through the recesses 89and radial holes 91 to the central bore through the cylinder 86 andthence longitudinally thereof. Similarly, the points 94 may be connectedto serve as voltage contacts by leads extending through the recesses 03and passages 98 to the central bore. The manner of using the device ofFigures 15 through 17 is the same as has already been described withreference to Figure 1.

Figure 18 illustrates a further modification in which a testing device Iis provided with only two contact points IM and I02. The testing deviceI00, otherwise generally similar to that shown in Figure '1, including avoltmeter. I03 and a rheostat I 04. Instead of using a'self-containedcurrent source, however, the device I00 is provided with leads Iextending to an external current source. A testing device of the typeshown in Figure 18 is useful only in cases where the contact resistancebetween the points NH and I02 and the interior of the article or memberbeing tested is of the same order of magnitude as the resistance of theportion of the length of the latter between the contact points withadeiect such as a fracture therein. Under these conditions, theredistributiono-i the voltage-'applied-to the contact points I0;I and102 as between 'the actual points of contact thereof with the :memherbeing tested and the portion of the length of the latter between thepoints is :sufiicient :to give a change in the indication of thevoltmeter I03. The magnitude of the change in voltage indicated by thevoltmeter 103 is proportional to the current'being circulated :throughthememher being tested and his for this reason that leads I05 to anexternal current sourcexare provided so that relatively heavy currents:may :be employed.

It will be apparent from the foreging description and explanation thatthe various forms of testing device contemplated by my invention havethe common advantage that the current utilized circulates only throughthe particular member being tested and through only a small portion ofthe latter at any onetime. This makes possible the use of a currentsource of limited capacity and insures that suiiicient current *tooperate the detecting mechanism will always be present in the particulararticle being tested. It will be appreciated that this is a distinctimprovement over prior testing devices contemplating the supply ofcurrent to a plurality .of articles simultaneously by-means ofseparate-terminals adapted to be applied to .membersin electricalcontact with a plurality of the articles to be tested. By myinvention,.I am able to test hollow articles satisfactorily with arelatively small current and I amalways assured that the testing currentpasses through the article under test, instead of being by-passedthrough adjacent parallel paths.

Although I have illustrated and described several forms which myinvention may take, it will beunderstood that chan es in theconstruction or arrangementof parts disclosed maybe made withoutdeparting from the spirit of the invention or the scope of the appendedclaims.

I claim:

1. Apparatus for testing hollow articlesof electrically conductingmaterial comprising an-elongated member insertible into said articles,contacts projecting laterally from said member and spaced longitudinallyand circumferentially-thereof, a current source connected to saidcontacts for circulating an electric current longitudinally andcircumferentially through an article when the member is inserted thereinso that said contacts engage the interior of the .article, and voltageeontacts on said member adapted when the member is inserted in thearticle .to engage the latter at points spaced along the path of saidcurrent.

2. Apparatus for testing hollow articles-of .electrically conductingmaterial comprising an elongated member insertible into said articles,contact brushes spaced along said member and projecting laterallytherefrom adapted to engage the article when the member is insertedtherein, each brush including a disc normal to said :member andelectrically conducting bristles extending outwardly therefromsubstantially throughout the periphery of the disc, a current source onsaid member connected to said brushes and voltage contacts spaced alongsaid member between said brushes and adapted'to engage the article whensaid member is inserted therein.

3. Apparatus as defined by claim 2 character- 9 ized by said discscomprising a plurality of segments mounted on said member.

4. Apparatus as defined by claim 3 character- The following referencesare of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 664,144 Gerhardt Dec. 18, 19001,104,753 Baluss July 21, 1914 1,253,282 Ruckardt Jan. 15, 1918 NumberNumber Name Date Heany Feb. 28, 1922 Kinnard Jan. 2, 1923 Gammeter Feb.3, 1925 Greenslade Dec. 29, 1925 Putnam Jan. 31, 1933 Greenslade Aug.31, 1937 Drain Sep. 28, 1937 Kohler Nov. 5, 1940 FOREIGN PATENTS CountryDate Germany July 5, 1915 OTHER REFERENCES Electrical World, Aug. 8,1925, pp. 257-259.

